Generally, a currently ongoing LTE-A system supports carrier aggregation (CA) as a means for increasing spectrum efficiency and throughput. In this carrier aggregation, a bandwidth is extended by aggregating a plurality of carriers to raise a data rate.
Multicarrier indicates the whole frequency bands used by a base station. And, a component carrier means an element carrier that constructs the multicarrier. In particular, a plurality of component carriers construct the multicarrier via the carrier aggregation.
In a general frequency division duplex (FDD) wireless communication system, data transceiving is performed via one downlink band and one corresponding uplink band. In the carrier aggregation applied wireless communication, a bandwidth is configured by aggregating a plurality of component carriers to support large and various uplink/downlink bandwidths. For instance, in LTE-A system, 5 component carriers of maximum bandwidth 20 MHz are aggregated to support uplink/downlink (UL/DL) bandwidth of 100 MHz.
Regarding the carrier aggregation (hereinafter abbreviated CA), there are continuous CA and non-continuous CA. In the continuous CA, component carriers continuously exist on a frequency axis. In the non-continuous CA, component carriers discontinuously exist on a frequency axis by being spaced apart from each other.
In the following description, a method of transmitting channel bandwidth information according to a related art is explained. FIG. 1 is a diagram for transmission bandwidth configuration of LTE system.
First of all, in the LTE system, a system bandwidth supports 1.25 MHz up to maximum 20 MHz. In case that the system bandwidth is 20 MHz, the number of maximum available resource blocks (RB) is 100 in consideration of interference between adjacent channels, transmission power leakage to an adjacent band and the like.
Referring to FIG. 1, if a channel bandwidth is 20 MHz, a transmission block configuration includes 100 resource blocks. And, active resource blocks means the resource blocks actually used by a mobile station among available resource blocks.
In the LTE system, a base station indicates a downlink channel bandwidth as the number of maximum available resource blocks via master information block (hereinafter abbreviated MIB) of PBCH.
FIG. 2 is a diagram of a master information block according to a related art.
Referring to FIG. 2, a variable d1-bandwidth indicates a channel bandwidth and the d1-bandwidth can be set to a value corresponding to one of n6, n15, n25, n50, n75 and n100. In the LTE system, if a system bandwidth is 1.4 MHz, the number of maximum available resource blocks is 6. If a system bandwidth is 3 MHz, the number of maximum available resource blocks is 15. If a system bandwidth is 5 MHz, the number of maximum available resource blocks is 25. If a system bandwidth is 10 MHz, the number of maximum available resource blocks is 50. If a system bandwidth is 15 MHz, the number of maximum available resource blocks is 75. If a system bandwidth is 20 MHz, the number of maximum available resource blocks is 100. Hence, according to a related art, a base station is able to indicate a channel bandwidth by informing a mobile station of the number of available resource blocks.
In case that the LTE-A system uses the continuous carrier aggregation, it is able to reduce a band unused between a guard interval belonging to a component carrier and the component carrier. When each of the component carriers has a bandwidth of 20 MHz, 108 resource blocks for each of the component carriers are usable for data transmission.
Therefore, n108 should be added as a value available for the d1-bandwidth. Yet, if the value available for the d1-bandwidth is increased, it causes a problem that backward compatibility is not maintained. In particular, on condition that: the continuous carrier aggregation is applied; a bandwidth of the component carrier is 20 MHz; and the LTE mobile station and the LTE-A mobile station coexist in the same cell, if a base station transmits n108 as a value of the d1-bandwidth, the LTE mobile station is unable to interpret the value. If the base station transmits n100 as a value of the d1-bandwidth, the LTE-A mobile station is unable to use 8 resource blocks.